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Old 05-22-2010, 01:13 AM
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Piston Rings 5/64 Vs 1/16

I ordered an Eagle 383 balanced rotating assembly part # B13004L153.It was listed on their site coming with KB-135 hypereutectic -18.0cc inverted dome pistons ring size: 5/64" 5/64".
But when I received it today it came with KB-102 pistons that are the same as the KB135 but use 1/16 in.x 3/16 in rings.I got the correct size rings for KB 102 (Total Seal # CR3690-30)
My question is what is the difference between the two beside the size.It's going to my 70 El Camino which just going to be street car.Are the rings and pistons going to be ok with my application.
I wanted to find out the opinions here if have anything to complain about before I complain.
http://www.eaglerod.com/index.php?op...d=21&Itemid=32
http://www.summitracing.com/parts/TSR-CR3690-30-1/
http://www.summitracing.com/parts/UEM-KB102-030/
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Old 05-22-2010, 01:29 AM
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In the real world, it's probably just 6 of one and half-a-dozen of the other. There are those who prefer the wider ring on a low rpm motor, thinking that maybe they seal a little better with more surface area riding on the cylinder wall. Then there are the top end guys who want to use a thinner, lighter ring to rev a competition motor higher without floating the rings. Lighter rings tend to conform to the ring lands and seal better at higher r's. Or so I've been told. Of course I don't have the equipment to test these theories.

Bottom line for me: I wouldn't walk across the street to change out one for the other in a street/strip motor.
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Old 05-22-2010, 05:12 AM
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I usually reccommend the wider rings on a street motor. Mostly based on cost. The narrow rings can get real spendy on bores larger than 4.125.
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Old 05-22-2010, 12:53 PM
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Quote:
Originally Posted by Dino383
I ordered an Eagle 383 balanced rotating assembly part # B13004L153.It was listed on their site coming with KB-135 hypereutectic -18.0cc inverted dome pistons ring size: 5/64" 5/64".
But when I received it today it came with KB-102 pistons that are the same as the KB135 but use 1/16 in.x 3/16 in rings.I got the correct size rings for KB 102 (Total Seal # CR3690-30)
My question is what is the difference between the two beside the size.It's going to my 70 El Camino which just going to be street car.Are the rings and pistons going to be ok with my application.
I wanted to find out the opinions here if have anything to complain about before I complain.
http://www.eaglerod.com/index.php?op...d=21&Itemid=32
http://www.summitracing.com/parts/TSR-CR3690-30-1/
http://www.summitracing.com/parts/UEM-KB102-030/
I think what you get into is ring tension issues where race motors can get by with a narrower ring as the blow-by pressures are higher and the crankcase positively vented. The blow-by can be harnessed to improve the ring's pressure against the cylinder wall, yet allow some relaxation of sealing wall pressure on the other strokes which gains some modest reduction of internal friction while the a thinner ring provides a small weight reduction to the moving masses as well. But to work best, they really require a positively vented crankcase, that's a vacuum pump or siphon to the exhaust, not a just PCV valve to keep the counter-pressures in the crankcase at negative pressure levels.

For a street engine the wider ring provides a better seal without the expectation of high amounts of blow-by pressure to force the rings into the wall and the ring is expected to work against a positive pressure in the crankcase at least some of the time. A lot of blow-by is not desirable on the street so high pressures form combustion are not available to boost ring tension, nor are positive crankcase pressure evacuation systems beyond a PCV valve so the ring has to make the force needed to keep the seal pretty much by itself. It sounds like you got the right pistons and rings for your intended street use.

Probably in the real world on the street it wouldn't make all that much difference which ring, especially when the engine was young. Maybe not even on the race track. Frankly, splitting hairs over ring tension is more a discussion for the dyno room where you can and do see a slight difference. That's considered to be enough to win races by most car owners. These days it's slight differences adding up to enough of a difference that makes certain builders more successful than others.

Bogie
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Old 05-22-2010, 01:20 PM
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Thanks for the info.I should given you more info in my first post.The 383 rotating kit is going in a 1970 El Camino,automatic trans,the compression is going to come in at around 9.6-9.7.I was planning to use vortec heads and a cam that will be compatible to give good low end torque.

This of course won't be a high RPM motor.The rings I received are standard 1/16 tension plasmamoly.Do you think these pistons and rings this will be ok with this combo.I was also under the impression that 1/16 rings were for higher reving motors but I know design and thinking have changed over the years.I was hoping to get started this weekend putting this engine together.But I want to hear so more I start it.

I didn't get the kit form Eagle directly I bought it through a
vendor like I said before call them I hoped get all the honest info from you guys.I don't want to call the on Monday and have them say yeah it's fine go ahead run it no problem just because thet don't want any hassel, and find later after build it that yeah I have do have problems.

I'm sorry if I seem dense on this issue,I have built motors in the past but all with 5/64 rings so the 1/16s have thrown me for a loop.

Thank you for all your posts and advice.
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Old 05-22-2010, 05:20 PM
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Don't worry about the ring width, it isn't really an issue. 1/16" is a better conforming ring, it will fit to the bore better than a wider ring. Since ring seal is only on a very small section of the edge of the ring, not fully acrossed the face, the width doesn't really matter.

There is no performance decrease or any other problem at lower rpm with thinner rings, they are just better at higher rpm than thicker rings.

The new generation GM V8's, the LS series stuff has 1.5mm rings, which is .059", just under 1/16".

The current street/strip and race standard is 1.5mm or even thinner .043" compression rings.
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Old 05-23-2010, 12:11 PM
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Thanks guys for all your input.I feel much better about it now.

I got this rotating kit from CNC Motorsports $835.95.It was $110.00 less than the same kit on Summit.
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